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Tim Pederson, lead hydronic expert for Cardinal Heating & Air Conditioning installs a Hydrofill NA570924 water-treatment unit at a commercial job site near Madison, Wisconsin. The unit removes minerals from water to make it better for the hydronic boiler systems.

Concerned about a growing number of premature heat-exchanger failures in customers' high-efficiency boilers, management at Cardinal Heating & Air Conditioning huddled with hydronic-system manufacturers and distributors to determine the cause.

The verdict: Excess minerals in water inside the hydronic systems were plugging up boilers' heat exchangers. The solution: A Hydrofill NA570924 water-treatment unit made by Caleffi.

“The passageways that water flows through in low-mass (wall-hung), high-efficiency boilers are a lot smaller,” explains Craig Ouimette, the service manager at Cardinal, based in Sun Prairie, located near Madison, Wisconsin. The company installs roughly 75 hydronic systems a year within about a 60-mile radius around Madison; about half are commercial and half are residential installations. “As such, they’re not as forgiving as the old cast iron boilers. So water quality has become a bigger issue — lime and calcium deposits, hard water and so forth.

“The Hydrofill basically takes virtually all the minerals out of the water, making it pure,” he continues. “It gives the hydronic system a fighting chance when you’re filling it with pure water and not introducing any extra minerals into the system. And since a hydronic system is a closed-loop system, the water that’s in the system stays in the system. So if you can first condition the water, it should help the boiler last for years to come.”

Even an extremely thin layer of lime deposit on a heat exchanger can decrease a boiler’s efficiency by as much as 20 percent. That’s because the lime acts as an insulator that prevents the burner from transferring heat to the water passing through it. “So instead of heating the water all the way, you lose more and more heat out the exhaust pipe,” he notes. “And if that thin layer builds up to, say, 1/4 of an inch thick, the metal (exchanger) runs a lot hotter than it otherwise would, which makes it flex at the welds. That’s where leaks start to develop.”

Here’s how it works: A technician connects a hose from an on-site water supply to a standard hose fitting on the bottom of the Hydrofill. The water then filters up through six resin bags filled with tiny mixed-resin beads charged with positive and negative ions. The beads filter impurities from the water. Then the water leaves the unit via another hose that’s connected to the hydronic system.

As the water passes through the Hydrofill, a highly accurate built-in meter monitors the level of totally dissolved solids (TDS), measured in parts per million (ppm). Tap water, for example, typically has a TDS level of 180 to 190 ppm. In a hydronic system, anything less than 30 ppm is considered a decent operating level. But the Hydrofill often attains levels of 5 to 10 ppm, Ouimette explains. “We can show that to customers right on the digital TDS meter,” he says.

The unit shuts off automatically after 10 minutes of non-use. It’s powered by a replaceable battery with a life of approximately 1,000 hours. Ouimette estimates that the resin bags need to be replaced about every 30 system fillings. He says Cardinal charges customers a modest add-on fee to essentially cover the cost of replacing the resin bags, which are made from a water-permeable material and come prepacked with beads. That makes replacing them quick and convenient: take the old bags out and put new ones in, he notes.

“It’s not a game-changer in terms of revenue,” he says. “We bought it more for adding value to system installations. A lot of customers have had a sour taste in their mouths because of all the issues they’ve experienced with high-efficiency units. They’re not sure the new system will be any better than the old one that failed. But once we flush a system and show them what’s coming out of their (water) piping, it’s an easy add-on sale.

“Our job as contractors is to educate them about why the previous unit failed, and explain why a little additional water-quality upgrade will save them a lot of headaches down the road,” he continues. “This component (the Hydrofill) is going to be huge for us because a lot of premature system failures in our area were due to water hardness, not installation errors.”

Cardinal rented a Hydrofill unit several times from Monroe Equipment, a Caleffi distributor, before buying one in late 2016 for about $1,400. While it’s not a huge revenue generator, it’s hard to put a price on expected higher levels of customer satisfaction in the years ahead as high-efficiency boilers start to reach their full life expectancy, rather than failing shortly after warranties expire, he says.

“The more we can do up front to protect that appliance, the more efficiently it will run and the longer it will last,” Ouimette concludes. “And that, in turn, means happier customers.”